1. Technical Field
The present invention relates generally to dental impression trays and, more specifically, to dental impression trays having a dental impression material retainer incorporated therein.
2. Description of the Related Art
EP 0 096 020 B1 discloses a dental impression tray comprising a trough for receiving dental impression material and a porous felt anchoring mat. The trough is provided on at least certain portions of its inside surface with the felt mat. The felt mat serves to hold the hardened impression material in the impression tray when the impression tray is removed from the jaw. The felt mat is made up of filaments which are distributed uniformly in all directions and which lie close to each other on the inside of the trough and are attached to the latter. The filaments are fixed to each other at their contact points so that a relatively stable three-dimensional network is formed.
To use this known impression tray a flowable impression material is first introduced into the trough and then the tray is placed on the patient's jaw and pressed against the teeth. In this way, the impression material is pressed with relatively great force against the felt mat on the inside of the trough, with the result that it penetrates into the outer layer of the felt mat and the filaments of the latter become embedded in the impression material.
One disadvantage of this known impression tray is that an impression material having a relatively high viscosity may penetrate only slightly into the felt mat. For this reason, only a few filaments located on the top of the felt mat may become embedded in the impression material and, as a consequence, may be easily torn out of the hardened impression material when the impression tray is removed from the jaw, because of the high tensile forces that occur during this procedure.
The impression material may push down and compress even a thick felt mat so there will be only a limited penetration of the impression material around the filaments of a thick mat. There is a risk of the impression material detaching from the impression tray and losing its original shape, as a result of which the subsequent dental work loses out on accuracy of fit.
It is further well known in the prior art to achieve a very good “retention capacity” (i.e., a measure of the bond strength between a dental impression material and a dental impression tray) by using a dental adhesive, for example a polyvinyl siloxane adhesive available from 3M ESPE AG, Germany, with a simple dental impression tray. The adhesive is first applied with a small brush to the inner surface of the trough. Then it must dry, typical drying times being between 3 and 6 minutes, and finally the impression material is introduced into the trough. This approach may provide a better retention capacity than the known dental impression tray described in EP 0 096 020 B1, but it requires the dental professional to perform the additional steps of applying an adhesive and waiting for the adhesive to dry.